Chronic pruritus affects millions of people worldwide and represents a serious and unmet medical need. The itch sensation is believed to be induced at least in part through the action of the endogenous neuropeptide substance P (SP), through the binding at NK-1Rs expressed on multiple skin cells.
The NK-1R is expressed throughout different tissues of the body, with major activity found in neuronal tissue. SP and NK-1R interactions in neuronal tissue regulate neurogenic inflammation locally and the pain perception pathway through the central nervous system. Other tissues, including endothelial cells and immune cells, have also exhibited SP and NK-1R activity. The activation of NK-1R by the natural ligand SP is involved in numerous physiological processes, including the perception of pain, behavioral stressors, cravings, and the processes of nausea and vomiting. An inappropriate over-expression of SP either in nervous tissue or peripherally could result in pathological conditions such as substance dependence, anxiety, nausea/vomiting, and pruritus. An NK-1R antagonist may possess the ability to reduce this over-stimulation of the NK-1R, and as a result address the underlying pathophysiology of the symptoms in these conditions.
Tradipitant is a neurokinin-1 receptor antagonist formerly known as VLY-686, having the chemical names 2-[1-[[3,5-bis(trifluoromethyl)phenyl]methyl]-5-(4-pyridinyl)-1H-1,2,3-triazol-4-yl]-3-pyridinyl](2-chlorophenyl)-methanone and {2-[1-(3,5-Bistrifluoromethylbenzyl)-5-pyridin-4-yl-1H-[1,2,3]triazol-4-yl]-pyridin-3-yl}-(2-chlorophenyl)-methanone, and the following chemical structure:
Tradipitant is disclosed in U.S. Pat. No. 7,320,994, and contains six main structural components: the 3,5-bis-trifluoromethylphenyl moiety, two pyridine rings, the triazol ring, the chlorophenyl ring and the methanone. Crystalline Forms IV and V of tradipitant are disclosed in U.S. Pat. No. 7,381,826. A process for synthesizing tradipitant is disclosed in U.S. Pat. No. 8,772,496.